The long-term goal is to better understand, explain, and predict human self-motion perception in three dimensions. Misperception of self-motion is a primary characteristic of vestibular disorders, and impacts patient symptom descriptions. However, patients often have difficulty explaining their confusing perceptions of motion, and tools are scarce for reporting perceived motion. In addition, even for healthy subjects, we cannot yet fully explain and predict the type and direction of perceived self-motion in many motion environments. This proposal focuses on self-motion perception in healthy subjects for whole-body passive motion in the dark. Current diagnostic techniques for vestibular disorders rely heavily on eye movements, but perception appears to deviate from eye movements in many cases. Of particular interest in this grant are perceptions that deviate from eye movements, and the grant's research combines experimental and modeling methods. The first aim is to identify patterns across experiments in differences between perceived self- motion and eye movements, while advancing the tools for comparing perception and eye movements. Without three-dimensional analysis, it may be impossible to determine whether complex perceptions and eye movements are compatible. This research will test several existing sets of experimental data through three-dimensional modeling. The results will be placed into a common framework to identify patterns across directions and types of motion. Besides determining whether various experimental results can be explained by three-dimensional factors, this research will test the hypothesis that perception differs from eye movements in a manner that is shared across axes and directions of motion. The second aim is to determine whether perception becomes predictive during periodic motion. Perceived motion is known to be out of phase with eye movements during periodic motion, but it is not known whether this phenomenon occurs because (1) perception switches to a predictive mode during periodic motion, or whether (2) perception differs from eye movements even during non-periodic motion. Experiments will compare perception during periodic and non-periodic tilt and translation. The research will compare perception with eye movements, as well as different directions of motion. An additional outcome will be the further development of three-dimensional modeling and animation tools for reporting, displaying and analyzing perceived self-motion. These capabilities will feed into the long-term goal of understanding self-motion perception in environments beyond those specifically studied here. The animations can also ultimately be use as tools for self-reports of motion, for both healthy subjects and vestibular patients. PUBLIC HEALTH RELEVANCE Vestibular disorders are typically accompanied by disorienting illusions of motion. This project aims to explain and predict illusions and misperception of self-motion in unusual motion environments through the use of three-dimensional modeling of experimental results.